GB834916A - Improvements in fuel systems for aircraft gas turbine engines - Google Patents

Abstract

834,916. Gas-turbine plant. DOWTY FUEL SYSTEMS Ltd. April 1, 1958 [Jan. 2, 1957], No. 227/57. Class 110 (3). [Also in Group XXIX] A variable stroke pump 13 supplies fuel to the burners of an aircraft gasturbine engine via pipes 12, 14, 78, a variable restriction constituted by a sliding valve 3 in a fuel/air ratio control unit 1 and a pressurizing valve 77; a by-pass circuit is provided from pipe 14 to the pump inlet by way of pipes 66, 56, a variable throttle valve 67 and a by-pass valve 55. The position of valve 3 is determined by a spring-loaded piston 16 under the control of a hinged leakoff valve 24 the opposite sides of one end being connected to bellows 28, 29, the former being acted upon compressor inlet or outlet pressure, and the latter being evacuated ; the other end of closure 24 is oppositely loaded by springs 26, 27, spring 26 abutting the valve 3. The pressure-drop of the fuel flowing through the valve 3 is applied to pads 36, 37 to set the position of another hinged leakoff valve 34 oppositely loaded by springs 39, 41, the latter being adjustable by a cam 42 rotated by a servomotor, not shown, to control the position of a piston 46 connected to the pump displacement control 48 and so effect variation of the fuel air ratio control. Engine speed is controlled by an all-speed governor 51 with a manual lever 52, which, through a half-ball valve 54, determines the position of a spring-loaded piston 62 attached to the closure 61 of the by-pass valve 55. The outlet port 8 of valve 3 is also connected by a passage 15 to another variable restriction constituted by an outlet port 11, which, through a pipe 76, opens into the spring chamber 73 of the valve 67, the closure 71 of which, in normal operation, is held from its seat 69 to interconnect pipes 14, 66. The closure 79 of valve 77 is loaded towards its seat 81 by a spring 82 and the pressure in pipe 76, the closure only seating when the flow rate to the burners approaches the minimum. When the lever 52 is moved to select a lower speed, or at idling, the greater part of the fuel from pipe 14 flows to pipe 56 and closure 79 seats so that the burner fuel then flows through port 11 and pipes 76, 78 the closure 71 preventing complete by-passing of the fuel to pipe 56. The variable restriction 11 of the minimumflow control may be operated by a separate servomotor; the control of the loading of the spring of valve 67 may also be effected by the latter or by the servomotor provided for the fuel/air ratio control.